Short answers, pulled from the story.
The Battle of Madagascar was an Allied campaign from the 5th of May to the 6th of November 1942 to capture the Vichy French-controlled island of Madagascar. The British objective was to deny the island's ports to the Imperial Japanese Navy and protect Allied shipping routes to India, Australia, and Southeast Asia. It was the first large-scale Allied operation of the war combining sea, land, and air forces.
Britain invaded Madagascar to prevent Imperial Japanese submarines from using the island's ports as forward bases. Japanese Kaidai-type submarines had a range of more than 10,000 miles, meaning Madagascan bases could threaten Allied supply lines from the Pacific to the South Atlantic. Japanese carrier raids on Ceylon and the Bay of Bengal in March 1942 made the threat immediate.
Operation Ironclad began on the 5th of May 1942 with British landings at Courrier Bay and Ambararata Bay near Diego-Suarez. After three days of fighting, including a bold destroyer raid that landed fifty Royal Marines inside Vichy defences, Antisarane surrendered on the evening of the 6th of May. The British suffered 109 killed and 283 wounded; Vichy French casualties totalled 700.
Yes. On the 29th of May 1942, three Japanese submarines arrived at Diego-Suarez. Midget submarines launched from I-20 and I-16 entered the harbour; one fired two torpedoes, seriously damaging the battleship Ramillies and sinking the oil tanker British Loyalty. The crew of one midget submarine, Lieutenant Saburo Akieda and Petty Officer Masami Takemoto, were killed by Royal Marines three days after beaching their craft.
The Battle of Madagascar lasted from the 5th of May 1942 to the 6th of November 1942, a total of six months. Fighting effectively ended when Vichy Governor General Armand Léon Annet, cornered near Ihosy in the south of the island, sent an envoy requesting surrender terms. An armistice was signed at Ambalavao on the 6th of November, and Annet surrendered two days later.
After the Allied victory, Madagascar was placed under Free French control. General Paul Legentilhomme was appointed High Commissioner in December 1942. In 1947 the island experienced the Malagasy Uprising, a revolution that was crushed in 1948. Madagascar did not achieve independence until the 26th of June 1960, when the Malagasy Republic was proclaimed.